As alkaline soluble resins, there have heretofore been known novolac resin, phenolic resin, and polymers having acrylic acid or methacrylic acid as a structural component, and they have been used in photo prints and as the resist materials for electronics industries, and among them many polymers have been put into practical use. The following is typical examples; UV lights including g-line light (wavelength of 436 nm) and i-line light (wavelength of 365 nm) have been used as an exposure source in lithography field and further excimer laser beams (KrF excimer laser beams; wavelength of 248 nm and ArF excimer laser beams; wavelength of 193 nm) have recently been used for this purpose, and as the base polymers of the resist materials, in accordance with the exposure source, novolac resin is mainly used as resist materials for g-line light and i-line light and phenolic resin is mainly used as resist materials for KrF, and both of those resins contain phenolic hydroxy groups (pKa of about 12) as functional groups which can be developed by an alkaline developing solution.
On the other hand, an acrylic acid derivative type or a methacrylic acid derivative type resins have mainly been used as a base polymer for ArF resist materials which have still been under developing stage (For instance, Japanese Patent Application Kokai (Laid-Open) Nos. (JP-A-) 7-199467, JP-A-8-82925 and JP-A-7-234511). The reason is that resins having aromatic rings so far being used is low in their transparency in far ultraviolet range and particularly it becomes completely non-transparent at the wavelength of ArF excimer laser beams, i.e. 193 nm. However, those resist materials wherein acrylic acid resin or methacrylic acid resin is used as the base polymer show high acidity (pKa of about 5) because a carboxylic group is used as a soluble group, which results in higher dissolving speed upon the development by alkaline substance as compared with known polymer wherein phenol groups are used as a soluble group, and therefore those resist materials are accompanied with such defects that a film is peeled off upon fine pattern formation and even non-exposured parts are dissolved out when a known alkaline developing solution, 2.38% tetramethylammonium hydroxide (TMAH), is used without diluting and thus no good pattern can be obtained.
Further, the main alkaline developing solution so far applied in actual production lines of semiconductor apparatuses is the above mentioned 2.38% TMAH, and it is actually very difficult to use the developing solution in diluted state in the production lines wherein resist materials belonging to different generations, such as both of i-line lights resist and KrF resist and both of KrF resist and ArF resist are applied together.